Many wellbore operations necessitate anchoring a tool within the wellbore. Such tools can include plugs, packers, hangers, casing patches, and the like (collectively referred to herein as downhole tools).
FIG. 1 illustrates a common mechanism for anchoring a downhole tool 100 in a wellbore 101. Wellbore 101 includes a tubular member 102 having an inner diameter (ID) 103. Tubular member 102 may be production tubing, casing, production liner or any other structure defining the walls of a wellbore. Wellbore 101 is illustrated as being substantially larger in diameter than downhole tool 100, but this is for illustration purposes only. Generally, the downhole tool 101 would have a diameter only slightly smaller than ID 103 of tubular member 102.
Downhole tool 100 includes a mandrel 104 having cone-shaped protrusions 105 and 106 and a sealing section 107. Cone-shaped protrusions 105 and 106 can slide over the mandrel 104 and make contact with sealing section 107 via surfaces 108 and 109, respectively. Sealing section 107 is typically made of a deformable or otherwise malleable material, such as plastic, metal, an elastomer or the like.
Downhole tool 100 further includes a base section 110 attached to the mandrel 104 via a threaded section 111. Base section 110 can apply pressure to cone-shaped protrusion 105 via slips 112 when the mandrel 104 is moved in an upward direction 113. Cone-shaped protrusion 105 consequently slides up and over the mandrel 104, applying pressure to the sealing section 107. Downward pressure 114 to slips 115 (usually exerted by a sleeve 120) likewise transfers pressure to the sealing member 107 as the cone-shaped protrusion 106 slides downward. Sealing member 107 deforms and expands due to lateral pressure 116 (with force line indicated), as the sealing member 107 is squeezed between the cone-shaped protrusions 105 and 106. Ultimately, the sealing member expands to form a seal with the ID 103 of tubular member 102.
Once the lateral pressure 116 of the sealing member 107 against the ID 103 exceeds a certain calibrated value, continued squeezing (i.e., 113 and 114) causes the slips 112 and 115 to ride up on the cone-shaped protrusions 105 and 106, respectively. Slips 112 and 115 are also commonly referred to in the art as “dogs.” Upwardly stroking of the bottom dog (i.e., slip 112) causes the dog to ride up the cone-shaped protrusion 105 and to deform outwardly, indicated by the illustrated force arrow 117. Ultimately, the dog (i.e., slip) 112 will deform outwardly enough that the teeth 112a of the dog (i.e., slip) will bite into the ID 103. Likewise, continued downward pressure 114 on the slip 115 will cause the slip 115 to deform outwardly (indicated by the illustrated force arrow 118). Thus, downwardly stroking the top dog (top slip 115) causes it to bite into the ID 103 with teeth 115a. In the deployed configuration, the downhole tool 100 is anchored within the wellbore 101 by lateral pressure of the sealing section 107 and by the friction of the slips 112 and 115 biting into the ID 103 (via teeth 112a and 115a, respectively).
Tools, such as the generic downhole tool 100, must be deployed within a wellbore using a setting tool. (Note the distinction between the term “setting tool” and the term “downhole tool.” As used herein, a “setting tool” refers to a tool that is used to deploy a “downhole tool” within a wellbore). The setting tool carries the downhole tool 100 to the desired location within the wellbore and also actuates the mechanisms (e.g., applies forces 113 and 114) that anchor the downhole tool within the wellbore. To deploy a downhole tool within a wellbore, a setting tool is typically connected to the downhole tool and the pair of tools (i.e., setting tool and downhole tool) is run down the wellbore using a slickline, coiled tubing, or other conveying method. Once the pair of tools reaches the desired depth within the wellbore, the setting tool deploys the downhole tool by actuating the forces described above.
A variety of types of setting tools that operate according to a variety of designs are known in the art. Setting tools differ from one another with regard to the method by which they produce the output needed to actuate the downhole tools and, consequently, the amount of force they are capable of producing. Examples of force generating methods include hydraulic, electromechanical, mechanical, and pyrotechnic (explosive) methods. Each type of setting tool has associated advantages and disadvantages. For example, a disadvantage of hydraulic setting tools is that they generally require that fluid be pumped to the tool from the surface to pressurize and actuate the tool's setting mechanisms. By contrast, a pyrotechnic-based setting tool may be actuated using a timer or condition sensor that is contained within the setting tool itself, allowing the setting tool to operate without communicating with the surface to activate the setting tool. Examples of condition sensors include sensors that monitor acceleration, hydrostatic pressure, temperature, or a combination of these or other conditions. Once the requisite programmed conditions are met, a detonator within the setting tool can activate, and deploy the downhole tool, without needing to receive instructions from the surface.
Pyrotechnic-based setting tools have several problems. One problem is that the highly explosive materials they require to operate are generally dangerous and are typically subject to import/export and travel restrictions. Also, the setting tool can remain pressurized following detonation and must be depressurized by bleeding off pressure from the tool, by rupturing a bleed off mechanism at the surface—an operation that can be hazardous. Still further, and as explained in more detail below, pyrotechnic-type setting tools produce pressure in an explosive manner. The impulse generated by the rapid expansion of gases upon detonation in such a setting tool may not generate the optimum pressure for deploying downhole tools. Basically, the explosion may generate too much over pressure, over too short of a time, to properly set the downhole tool. Consequently, the force of the explosion must be throttled or dampened—a function typically performed using an internal hydraulic transducing mechanism. But such tools are limited in their application because they can only produce adequate force over short distances.
Accordingly, there remains a need in the art for a more versatile setting tool.